A. Kasten

Magnetic ordering in GdI2

GdI2 powder samples have been investigated by means of a.c. susceptibility and magnetisation measurements indicating magnetic ordering below TC = 313 K. The structure consists of strongly coupled ferromagnetic layers of Gd3+ moments aligned perpendicular to the hexagonal crystal axis. The inter-layer coupling is much weaker and probably antiferromagnetic suggesting that GdI2 is to a very good approximation a two-dimensional Heisenberg system.

Ferrimagnetic phase in the metamagnet DyVO4

Abstract In the Ising antiferromagnet DyVO4 a new intermediate ferrimagnetic phase has been found at the metamagnetic transition from the antiferromagnetic to the paramagnetic state below 1.27 K. Although this new phase extends only over a field range of about 1 mT, it is clearly seen in specific heat experiments since for crystals with finite demagnetising factor it produces additional mixed phases at the first order phase boundaries. The ferrimagnetic state is established by antiferromagnetic further-than-nearest neighbour interaction which is quite common in metamagnets with dipole interaction. The possibility of even more intermediate phases and the general problem of first order metamagnetic transitions is discussed.

Extensive studies on the low-temperature properties of TbPO4. I: Magnetic measurements

At low temperatures, TbPO4 shows two phases with antiferromagnetic ordering in immediate succession, the upper one with tetragonal and the lower one with monoclinic crystal symmetry. Magnetisation and magnetic susceptibility were measured in the region of these phases for different external field directions. One main aspect was to study the anisotropy of the susceptibility for a single-domain crystal in one of the low-symmetry phases. Unexpectedly, it turned out that the susceptibility is isotropic in the basal plane.

Crystal-field spectra of trivalent holmium in HoVO4, HoAsO4, HoPO4 and Y(OH)3 in the infrared region

The polarized absorption spectra of Ho3+ in HoVO4, HoAsO4, HoPO4 and (Ho0.1,Y0.9) (OH)3 were studied in the range from 5000 to 12000 cm-1. Nearly all crystal-field components were found and their crystal quantum numbers mu , nu and S could be assigned.